Polymers photostabilized by novel imidazole-2-carboxanilides

ABSTRACT

Photostabilized polymers, including polyurethanes and plastics coatings, contain as photostabilizer one or more compounds of the formula ##STR1## or a novel imidazole-2-carboxanilide of the formula ##STR2##

U.S. Pat. Nos. 3,907,700 and 4,011,236 disclose N-(benzimidazol-2-yl)arylcarboxamides of the formula (X) ##STR3## as UV stabilizers for organic polymers. However, these amides provide inadequate stabilization, for example in polyurethane. A further disadvantage is the incompatibility with many plastics, the volatility, and the discoloration of the polymeric substrates after incorporation of the amides.

It is an object of the present invention to provide compounds which have high absorption in the wavelength range 280-400 nm, low volatility and little tendency to discolor on thermal processing.

U.S. Pat. Nos. 3,740,413 and 3,661,925 disclose benzimidazole-2-carboxanilides as pharmaceutically active compounds. Further benzimidazole-2-carboxanilides and 4,5-diphenylimidazole-2-carboxanilides are described in French Patent No. 1,517,719, Chem. Ber. 92 (1959), 550, J. Chem. Soc. Sect. C 1967, 20, CA 101, 23395a and CA 98, 143322r.

We have found that the aromatic imidazole-2-carboxanilides of the invention meet this object and are highly suitable for photostabilizing organic materials.

The present invention accordingly provides a photostabilized polymer containing as photo-stabilizer one or more compounds of the general formula (I) ##STR4## where

n is 1 or 2,

R¹ and R² or one of the radicals R¹ or R² are each independently of the other phenyl or hetaryl which each may be substituted by C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, halogen or trifluoromethyl, and the other of the radicals R¹ or R² is hydrogen, C₁ -C₁₂ -alkyl, C₇ -C₉ -phenalkyl or --COOR⁵, where R⁵ is linear or branched C₁ -C₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl, where cycloalkyl and phenyl may be substituted by C₁ -C₄ -alkyl, or ##STR5## is a fused-on benzene ring which may be substituted by hydroxy, halogen, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, C₇ -C₉ -phenylalkyl, phenyl, --COOR⁶, --CO--R⁶, --CO--NH--R⁶, --COOH, --O--COR⁶, --NH--CO--R⁶, --SO₂ --R⁶ or --CN, where R⁶ is linear or branched C₁ -C₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl and the cycloalkyl and phenyl radicals may be substituted by C₁ -C₄ -alkyl,

R³ and R⁴ are each hydrogen or one of the radicals R³ or R⁴ is C₁ -C₄ -alkyl or C₇ -C₉ -phenalkyl and,

if n is 1,

X (a) is phenyl, naphthyl or a 5- or 6-membered aromatic, possibly benzofused, heterocyclic, these radicals being unsubstituted or monosubstituted or disubstituted by C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, phenoxy, C₇ -C₉ -phenylalkyloxy, C₇ -C₉ -phenylalkyl, trifluoromethyl, hydroxyl, halogen, --S--R⁷, --COR⁷, --COOR⁷, --COOH, --CN, --CONH--R⁷, --NH--R⁷, --N(R⁷)₂, --O--COR⁷ or --NH--COR⁷, where R⁷ is linear or branched C₁ -C₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl, in which cycloalkyl and phenyl may be substituted by C₁ -C₄ -alkyl, or if n is 2

X (b) is phenylene or naphthylene, these radicals being unsubstituted or substituted by C₁ --C₁₂ -alkyl, C₁ -C₁₂ -alkoxy or halogen, or

(c) a is a radical of the formula ##STR6## where Y is a radical of the formula --(CH₂)_(m), --CO--, --CO--(CH₂)_(p) CO--, --OCO--(CH₂)_(p) COO--, --NH--CO--(CH₂)_(p) --CO--NH--, --O--, ##STR7##

The photostabilized polymers of the invention, if compared with the compounds known from U.S. Pat. Nos. 3,907,700 and 4,011,236, which must be considered closest to those used according to the invention, show a superior action in long-term stabilization, a low volatility, a reduced migration and an enhanced thermostability.

For instance, the compound of Example 12 gives a highly photostabilized polyurethane integral foam. The stabilization obtained hereby is substantially superior to that obtained with prior art stabilizers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, di(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and/or triethylene glycolbis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate.

Halogen is fluorine, preferably chlorine or bromine.

Suitable hetaryl for R₁ and R² is for example pyridyl, furyl, quinolyl and thiophenyl.

Preferably, R¹ and R² are each phenyl, pyridyl or furyl, these radicals being unsubstituted or substituted by C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, chlorine or bromine.

Preference is further given to compounds (I) where ##STR8## is a fused-on benzene ring which may be substituted as indicated above.

Preferred substituents on the fused-on benzene ring are chlorine, C₁ -C₆ -alkyl and C₁ -C₈ -alkoxy, such as methyl, ethyl, i-propyl, 2-butyl, tert.-butyl, amyl, hexyl, methoxy, ethoxy, i-propoxy, n-butoxy, pentoxy and hexoxy.

R³ and R⁴ are each hydrogen or one of the radicals R³ or R⁴ is C₁ -C₄ -alkyl or C₇ -C₉ -phenylalkyl, such as methyl, ethyl, n-propyl, n-butyl, benzyl, 2-phenyl-1-ethyl or 2-phenyl-2-propyl. R³ and R⁴ are preferably each hydrogen.

The meaning of X depends on whether n is 1 or 2.

If n is 1, then X is phenyl, naphthyl or a 5- or 6-membered aromatic, possibly benzofused, heterocyclic, the radicals mentioned being unsubstituted or monosubstituted or disubstituted as stated above. Of these compounds (I) preference is given to those where X is unsubstituted, monosubstituted or disubstituted phenyl.

Preferably X is phenyl substituted by linear or branched C₁ -C₁₂ -alkyl, trifluoromethyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, C₇ -C₉ -phenalkyl, phenoxy, phenyl, C₁ -C-₁₂ -alkoxycarbonyl, C₁ -C₁₂ -alkylcarbonyl, benzoyl, cyano, N,N-di-C₁ -C₆ -alkylamino, C₁ -C₁₂ -alkyl-carbonylamino, C₁ -C₁₂ -alkanoyloxy, benzoyloxy, C₇ -C₉ -phenalkanoyloxy or chlorine, the number of substituents being 1 or 2.

Specific examples of substituents on the phenyl radical X, in addition to those specified, are:

(α) alkyl such as methyl, ethyl, n- and i-propyl, n-butyl, 2-butyl, tert.-butyl, n-pentyl, tert.-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl and n-dodecyl;

(β) alkoxy such as methoxy, ethoxy, i-propoxy, n-butoxy, n-pentoxy, i-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, 2-ethylhexoxy, n-nonoxy, n-decoxy and n-dodecoxy;

(γ) phenoxy, benzyloxy, 2-phenylethoxy, 3-phenylpropoxy.

Particular preference is given to compounds (I) where n=1 and where X is 4-C₁ -C₁₂ -alkylphenyl, 4-C₁ -C₁₂ -alkoxyphenyl, 4-phenoxyphenyl, 4-C₁ -C₁₂ -alkylcarbonylaminophenyl or 4-C₁ -C₁₂ -alkanoyloxyphenyl.

If n is 2, then X is either (b) unsubstituted or alkyl- or alkoxy-substituted phenylene or naphthylene or (c) a radical of the formula ##STR9## where Y has the abovementioned meanings. Preferably Y is --CH₂ --, --O-- or --SO₂ --.

If n is 2, preference is given to compounds (I) where X is unsubstituted or C₁ -C₁₂ -alkyl- or C₁ -C₁₂ -alkoxy-substituted phenylene or a radical of the formula II, the phenylene radicals in (II) being unsubstituted or substituted by C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy, although preferably unsubstituted, and Y is --CH₂ -- or --O--.

The present invention also relates to novel imidazole-2-carboxanilides of the formula (III) ##STR10## where the two Rs are each independently of the other ##STR11## R⁸ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, C₇ -C₉ -phenalkoxy, C₇ -C₉ -phenalkyl, trifluoromethyl, N,N-di-C₁ -C₆ -alkylamino, C₂ -C₁₂ -alkanoylamino, C₁ -C₁₂ -alkylcarbonyl, C₁ -C₁₂ -alkoxycarbonyl, benzoyl, cyano, methylenedioxy or ethylenedioxy, C₂ -C₁₂ -alkanoyloxy, benzoyloxy, C₇ -C₉ -phenalkanoyloxy,

R⁹ is C₁ -C₁₂ -alkyl, C₁ -C₄ -alkoxy, chlorine or hydrogen, T is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, trifluoromethyl, phenyl, C₇ -C₉ -phenalkyl or chlorine, and q is 1 or 2.

Preferably T is hydrogen, methyl or chlorine.

Of the compounds (III), preference is given to those of the formulae ##STR12## where R⁹ is methyl, methoxy or hydrogen,

R¹⁰ is C₁ -C₆ -alkyl, C₁ -C₄ -alkoxy or chlorine,

R¹¹ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, trifluoromethyl, N,N-di-C₁ -C₄ -alkylamino, C₂ -C₁₂ -acylamino, C₂ -C₁₂ -acyloxy, benzoyloxy or C₇ -C₉ -phenacyloxy,

T' is hydrogen, Chd 1-C₄ -alkyl or chlorine, preferably hydrogen, chlorine or methyl, and

q is 1 or 2.

The novel compounds of the formulae (III), (IIIa) and (IIIb) where R⁸, R¹⁰ and R¹¹ are linear C₈ -C₁₂ -alkoxy are highly suitable for stabilizing surface coatings, such as finished coats, and two-layer metallic effect coatings. The addition of these stabilizers substantially improves the performance fastness, in particular the light and weather fastness, of pigmented industrial coatings.

The compounds of the formulae (I), (III), (IIIa) and (IIIb) can be prepared in a conventional manner.

If R¹ and R² in (I) are a fused-on benzene ring, these compounds can be synthesized by condensing an o-phenylenediamine derivative of the formula (V) ##STR13## with an ethyl oxamate of the formula VI ##STR14## as described in French Pat. No. 1,517,719 and Bull. Soc. Chim. 10 (1966), 3368.

A further method of synthesis comprises reacting benzimidazole-2-carboxylic acid derivatives with aromatic amines:

(i) if R⁸ is an electron-withdrawing substituent, by reacting the 2-trichlorobenzimidazole derivative (VII) ##STR15## with an aromatic amine of the formula (VIII) ##STR16## as described in J. Chem. Soc. Sect. C., 1967, 20, and (ii) if R⁸ is an electron donor substituent, by reacting a dibenzoimidazo(1,2-a,1',2'-d)tetrahydropyrazine-6,13-dione derivative of the formula (IX) ##STR17## with an aromatic amine of the formula VIII, analogously to the reaction described in Indian J. Chem. 18B (1979), 464.

Furthermore, the compounds of the formula (I) are readily accessible by reacting an imidazole derivative of the formula (X) ##STR18## with an aromatic isocyanate of the formula (XI) ##STR19## The reaction is similar to that described in Chem. Ber. 92 (1959), 550.

The compounds (I), (III), (IIIa) and (IIIb) are incorporated in the polymers in a conventional manner.

For example, the compounds can be incorporated by mixing them with or without further additives into the melt in a conventional manner before or during shaping, or, alternatively, by applying the dissolved or dispersed compounds to the polymer directly or by mixing into a solution, suspension or emulsion of the polymer, and if necessary allowing the solvent to evaporate.

Examples of polymers to be stabilized are: polyolefins, polystyrene, styrene polymers, halogen-containing vinyl polymers, polyacrylates, polymethacrylates, polyacrylamides, polyacrylonitrile, polyvinyl alcohol and acyl derivatives thereof, polyacetates, polyalkylene oxides, polyphenylene oxides, polyurethanes and polyureas, polysulfones, polyamides, polyesters, polycarbonates, crosslinked polymers of aldehydes and phenols, urea and/or melamine, unsaturated polyester resins, alkyd resins, and thermosetting and thermoplastic acrylic resins.

The stabilizers according to the invention are mixed into the polymers individually or mixed in amounts of from 0.01 to 5, preferably from 0.05 to 2.5, in particular from 0.1 to 2, percent by weight, based on the material to be stabilized.

The materials thus stabilized can be converted into the customary application forms, for example films, fibers, ribbons or profiles, or may be used as binders for paints, adhesives, cements or molding compositions.

In practice the compounds of the formula I can be used together with from 0.1 to 5, preferably from 0.5 to 3, % by weight of further customary additives, such as antioxidants, further light stabilizers or mixtures thereof.

Examples of these customary additives are: antioxidants, UV absorbers and light stabilizers such as 2-(2'-hydroxyphenyl)benzotriazole, 2,4-bis(2'-hydroxyphenyl)-6-alkyl-s-triazine, 2-hydroxybenzophenone, 1,3-bis(2'-hydroxybenzoyl)benzenes, esters of substituted or unsubstituted benzoic acids, acrylates, and also nickel compounds, sterically hindered amines, metal deactivators, phosphites, peroxide-destroying compounds, polyamide stabilizers, basic costabilizers, nucleating agents and other additives such as plasticizers, lubricants, emulsifiers, fillers, carbon black, kaolin, talc, glass fibers, pigments, optical brighteners, flame retardants and antistatics.

The compounds of the formula (I) are suitable in particular for stabilizing polyurethanes derived from polyethers, polyesters and polybutadienes having terminal hydroxyl groups and aliphatic or aromatic polyisocyanates, and intermediates thereof, to degradation due to heat and in particular due to light.

An improved stabilizing action is obtained if a known antioxidant, for example a compound based on sterically hindered phenols, or a sulfur- or phosphorus-containing costabilizer is used in addition.

Examples of such phenolic antioxidants are 2,6-di-tert.-butyl-4-methylphenol, n-octadecyl β-(3,5-di-tert.-butyl-4-hydroxyphenyl)propionate, 1,1,3-tris(2'-methyl-4'-hydroxy-5'-tert.-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3',5'-di-tert.-butyl4'-hydroxybenzyl)-benzene, 1,3,5-tris(3',5'-di-tert.-butyl-4'-hydroxybenzyl)isocyanurate, 1,3,5-tris[3',5'-di-tert.-butyl-4'-hydroxyphenyl)propionyloxyethyl]isocyanurate, 1,3,5-tris(2',6'-di-methyl-3'-hydroxy-4'-tert.-butylbenzyl)isocyanurate, pentaerythritol tetrakis[β-(3,5-di-tert.-butyl-4-hydroxyphenyl)propionate], triethylene glycol bis-3-(3'-t-butyl-4'-hydroxy-5'-methylphenyl)propionate, derivatives of 6-hydroxy-2,5,7,8-tetramethylchroman such as α-tocopherol and (6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)ethyl stearate.

Examples of phosphorus-containing antioxidants are: trisnonylphenyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert.-butylphenyl)phosphite, tris(2-tert.-butyl-4-methylphenyl)phosphite, bis(2,4-di-tert.-butylphenyl)pentaerythritol diphosphite and tetrakis(2,4-di-tert.-butylphenyl)4,4'-biphenylene diphosphite.

Examples of sulfur-containing antioxidants are dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol tetrakis(β-laurylthiopropionate), and pentaerythritol tetrakis(β-hexylthiopropionate).

Particularly good stabilization is obtained by adding to the compounds of the formula (I), (III), (IIIa) and (IIIb) one or more light stabilizers from the class of sterically hindered amines in a customary concentration.

Examples of sterically hindered amines are: bis(2,2,6,6-tetramethylpiperidyl)sebacate, bis(1,2,2,6,6-pentamethylpiperidyl)sebacate, bis(1,2,2,6,6-pentamethylpiperidyl)esters, the condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, the condensation product of N,N'-(2,2,6,6-tetramethylpiperidyl)hexamethylenediamine and 4-tert.-octylamino-2,6-dichloro-1,3,5-s-triazine, tris(2,2,6,6-tetramethylpiperidyl)nitrilotriacetate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylic acid, 1,1'-(1,2-ethanediyl)bis(3,3,5,5-tetramethylpiperazinone), and the condensation products of 4-amino-2,2,6,6-tetramethylpiperidines and tetramethylolacetylenediureas.

Especially good stabilization of polyurethanes is obtained if the polyurethane contains a mixture of one or more compounds of the formula (I), one or more of the abovementiond antioxidants and one or more compounds of a sterically hindered amine. The Examples which follow will additionally explain the invention.

(A) PREPARATION EXAMPLES EXAMPLE 1

20.7 g (0.1 mol) of ethyl N-(4-methylphenyl)oxamate and 10.8 g (0.1 mol) of o-phenylenediamine are refluxed under nitrogen in 50 ml of dry dimethylformamide for 8 hours. After cooling down, 200 ml of methanol and 140 g of ice are added. The resulting precipitate is filtered off with suction and washed with a 1:1 mixture of methanol and water. Recrystallization from ethanol in the presence of active carbon gives 9.5 g of a colorless product of formula ##STR20## having a melting point of 226°-227° C.

Analysis: C₁₅ H₁₃ N₃ O (251.3). calculated: C 71.69, H 5.21, N 16.72, O 6.37. found: C 71.6, H 5.5, N 16.2, O 7.0.

EXAMPLES 2 TO 11

Practicing procedures analogous to that of Example 1 on appropriate starting materials gives the compounds listed in Table 1.

                  TABLE 1                                                          ______________________________________                                          ##STR21##                                                                     Example   T          R.sup.8     m.p. [°C.]                             ______________________________________                                         2         H          4'-C.sub.2 H.sub.5                                                                         219                                           3         H          2'-C.sub.2 H.sub.5                                                                         200                                           4         H          4'-i-C.sub.3 H.sub.7                                                                       222                                           5         H          4'-t-C.sub.4 H.sub.9                                                                       235                                           6         H          2',5'-(t-C.sub.4 H.sub.9).sub.2                                                            224-226                                       7         H          2'-OC.sub.2 H.sub.5                                                                        219-220                                       8         5/6-CH.sub.3 *                                                                            4'-t-C.sub.4 H.sub.9                                                                       211-213                                       9         5/6-CH.sub.3 *                                                                            4'-i-C.sub.3 H.sub.7                                                                       247-249                                       10        5/6-CH.sub.3 *                                                                            2',5'-(OC.sub.2 H.sub.5).sub.2                                                             212-215                                       11        5/6-CH.sub.3 *                                                                            4'-CO.sub.2 C.sub.2 H.sub.5                                                                207-208                                       ______________________________________                                          *Mixture of 5 and 6methyl compound                                       

EXAMPLE 12

14.4 g (0.05 mol) of dibenzimidazo(1,2a,1',2'-d)tetrahydropyrazine-6,13-dione and 14.8 g (0.11 mol) of p-phenetidine are heated under reflux in 80 ml of dimethylformamide for 3.5 hours. After dilution with 300 ml of methanol the precipitated product is filtered off with suction and washed with methanol to give 18.0 g of the benzimidazole-2-carboxanilide of the formula ##STR22## Melting point 201°-202° C.

Analysis: C₁₆ H₁₅ N₃ O₂ (281.21). calculated: C 68.31, H 5.37, N 14.94, O 11.37. found: C 68.2, H 5.5, N 14.9, O 11.3.

EXAMPLES 13 TO 32

Practicing procedures analogous to that of Example 12 on appropriate starting materials gives the compounds mentioned in Table 2.

    ______________________________________                                          ##STR23##                                                                     Example     R.sup.8        m.p. [°C.]                                   ______________________________________                                         13          4'-OCH.sub.3   237-239                                             14          3'-OC.sub.2 H.sub.5                                                                           211-213                                             15          4'-OC.sub.4 H.sub.9n                                                                          163-165                                             16          4'-OC.sub.6 H.sub.13n                                                                         151-153                                             17          4'-OC.sub.8 H.sub.17n                                                                         143-145                                             18          4'-OC.sub.12 H.sub.25n                                                                        141-142                                             19          2',5'-(OC.sub.2 H.sub.5).sub.2                                                                243-244                                             20          3',4'-OCH.sub.2O                                                                              262-264                                             21          3',4'-O(CH.sub.2).sub.2O                                                                      268-270                                             22          4'-C.sub.10 H.sub.21n                                                                         140-141                                             23          4'-C.sub.12 H.sub.25n                                                                         130-131                                             24          4'-N(CH.sub.3).sub.2                                                                          253-254                                             25          3'-CF.sub.3    203                                                 26          4'-NHCOCH.sub.3                                                                               308                                                 27          2'-OC.sub.4 H.sub.9n                                                                          183-184                                             28          2'-OC.sub.6 H.sub.13n                                                                         175-176                                             29          2'-OC.sub.8 H.sub.17n                                                                         160-163                                             30          2'-OC.sub.12 H.sub.25n                                                                        145-146                                             31          4'-OC.sub.6 H.sub.5                                                                           237-239                                             32          3',4'-(OCH.sub.3).sub.2                                                                       209                                                 ______________________________________                                    

EXAMPLE 33

23.6 g (0.1 mol) of 2-trichloromethylenzimidazole and 19.7 g (0.1 mol) of 4-aminobenzophenone are heated under reflux in 220 g of 14% strength hydrochloric acid for 5 hours. After cooling down, the precipitated product is filtered off with suction and washed with acetone. The residue is dissolved in 800 ml of ethanol and 50 ml of 20% strength sodium hydroxide solution, and the solution is then poured onto 2 l of ice-water. The precipitated solid is filtered off with suction and washed neutral with water. Drying leaves 17.6 g of colorless product of the formula ##STR24## Melting point 230°-231° C.

Analysis: C₂₁ H₁₅ N₃ O₂ (341.37). calculated: C 73.89, H 4.42, N 12.31, O 9.37. found: C 73.9, H 4.3, N 12.1, O 9.4.

EXAMPLES 34 TO 37

The compounds indicated in Table 3 were prepared by procedues analogous to that of Example 33.

                  TABLE 3                                                          ______________________________________                                          ##STR25##                                                                     Example       R.sup.8    m.p. [°C.]                                     ______________________________________                                         34            2'-COC.sub.6 H.sub.5                                                                      250-252                                               35            4'-CO.sub.2 C.sub.2 H.sub.5                                                               214-215                                               36            4'-CN      302-303                                               37            2',4'-(Cl).sub.2                                                                          304                                                   ______________________________________                                    

EXAMPLE 38

11.8 g (0.1 mol) of benzimidazole and 21 g (0.12 mol) of 4-n-butylphenyl isocyanate were heated under reflux in 180 ml of dry nitrobenzene for 6 hours. Cooling down resulted in the formation of a precipitate, which was filtered off with suction and washed with nitrobenzene and methanol to give 20.5 g of a colorless solid of the formula ##STR26## Melting point 205°-206° C.

Analysis: C₁₈ H₁₉ N₃ O (293.4). calculated: C 73.69, H 6.53, N 14.32, O 5.45. found: C 73.9, H 6.8, N 14.1, O 5.5.

EXAMPLES 39 TO 71

Practicing procedures analogous to that of Example 38 on the imidazoles and isocyanates indicated in Table 4 gave the corresponding imidazole-2-carboxanilines.

                                      TABLE 4                                      __________________________________________________________________________     Example                                                                             Imidazole derivative                                                                               Isocyanate                  Melting point                                                                  [°C.]              __________________________________________________________________________     39                                                                                   ##STR27##                                                                                          ##STR28##                  230-231                   40                                                                                   ##STR29##                                                                                          ##STR30##                  264-265                   41                                                                                   ##STR31##                                                                                          ##STR32##                  282-285                   42                                                                                   ##STR33##                                                                                          ##STR34##                  248-250                   43                                                                                   ##STR35##                                                                                          ##STR36##                  244                       44                                                                                   ##STR37##                                                                                          ##STR38##                  264                       45                                                                                   ##STR39##                                                                                          ##STR40##                  290-292                   46                                                                                   ##STR41##                                                                                          ##STR42##                  223                       47                                                                                   ##STR43##                                                                                          ##STR44##                  237-239                   48                                                                                   ##STR45##                                                                                          ##STR46##                  186-189                   49                                                                                   ##STR47##                                                                                          ##STR48##                  327                       50                                                                                   ##STR49##                                                                                          ##STR50##                  350 (dec.)                51                                                                                   ##STR51##                                                                                          ##STR52##                  236-238                   52                                                                                   ##STR53##                                                                                          ##STR54##                  197-198                   53                                                                                   ##STR55##                                                                                          ##STR56##                  233-235                   54                                                                                   ##STR57##                                                                                          ##STR58##                  237-240                   55                                                                                   ##STR59##                                                                                          ##STR60##                  244-246                   56                                                                                   ##STR61##                                                                                          ##STR62##                  158-160                   57                                                                                   ##STR63##                                                                                          ##STR64##                  217-218                   58                                                                                   ##STR65##                                                                                          ##STR66##                  192                       59                                                                                   ##STR67##                                                                                          ##STR68##                  238-240                   60                                                                                   ##STR69##                                                                                          ##STR70##                  157-158                   61                                                                                   ##STR71##                                                                                          ##STR72##                  170-172                   62                                                                                   ##STR73##                                                                                          ##STR74##                  180-181                   63                                                                                   ##STR75##                                                                                          ##STR76##                  299                       64                                                                                   ##STR77##                                                                                          ##STR78##                  272                       65                                                                                   ##STR79##                                                                                          ##STR80##                  286                       66                                                                                   ##STR81##                                                                                          ##STR82##                  210-212                   67                                                                                   ##STR83##                                                                                          ##STR84##                  212                       68                                                                                   ##STR85##                                                                                          ##STR86##                  228-229                   69                                                                                   ##STR87##                                                                                          ##STR88##                  103                       70                                                                                   ##STR89##                                                                                          ##STR90##                  207-209                   71                                                                                   ##STR91##                                                                                          ##STR92##                  205-206                   __________________________________________________________________________

EXAMPLE 72

14.4 g (0.05 mol) of dibenzimidazo(1,2a,1',2'-d)tetrahydropyrazine-6,13-dione and 30 g (0.18 mol) of 4-propionylaminoaniline are heated under reflux in 70 ml of dry dimethylformamide for 3 hours. After cooling down, about 700 ml of methanol are added. The precipitated solid is filtered off with suction and washed with methanol and dried to leave 20.7 g of the benzimidazole-2-carboxanilide of the formula ##STR93## Melting point 289°-291° C.

Analysis: C₁₇ H₁₆ N₄ O₂ (308.34). calculated: C 66.22, H 5.23, N 18.17, O 10.38. found: C 66.4, H 5.3, N 17.8, O 10.5.

EXAMPLES 73 TO 84

Practicing procedures analogous to that of Example 72 on appropriate starting materials gives the compounds indicated in Table 5.

                  TABLE 5                                                          ______________________________________                                          ##STR94##                                                                     Example                                                                               R.sup.8             Melting point [°C.]                          ______________________________________                                         73     NHCOt-C.sub.4 H.sub.9                                                                              258-260                                             74     NHCOCH(C.sub.2 H.sub.5)C.sub.4 H.sub.9n                                                            273-274                                             75                                                                                     ##STR95##          311-313                                             76     OC.sub.5 H.sub.11n  200                                                 77     OC.sub.5 H.sub.11i  220                                                 78     OC.sub.7 H.sub.15n  160                                                 79     OCH.sub.2CH(C.sub.2 H.sub.5)C.sub.4 H.sub.9n                                                       140                                                 80     OC.sub.9 H.sub.19n  150                                                 81     OC.sub.10 H.sub.21n 145                                                 82     OCH.sub.2C.sub.6 H.sub.5                                                                           217                                                 83     OCH.sub.2CH.sub.2C.sub.6 H.sub.5                                                                   194                                                 84     OH                  328-330                                             ______________________________________                                    

EXAMPLE 85

7.8 g (0.065 mol) of pivaloyl chloride are added dropwise at from 25° to 50° C. to a solution of 12.7 g (0.05 mol) of 4'-hydroxybenzimidazole-2-carboxanilide (from Example 78) in 50 ml of dry pyridine and stirred in at 50° C. for 3 hours. The reaction solution is poured onto 300 ml of ice-water and 100 ml of concentrated hydrochloric acid and stirred in for 20 minutes. The precipitated solid is filtered off with suction and washed with water. Recrystallization from toluene gives 9.5 g of a colorless product of the formula ##STR96## Melting point 266°-267° C.

Analysis: C₁₉ H₁₉ N₃ O₃ (337.38). calculated: C 67.64, H 5.68, N 12.45, O 14.22. found: C 67.8, H 5.8, N 12.2, O 14.1.

EXAMPLES 86 TO 89

Procedures analogous to that of Example 85 gave the compounds listed in Table 6.

                  TABLE 6                                                          ______________________________________                                          ##STR97##                                                                     Example     R              m.p. [°C.]                                   ______________________________________                                         86          C.sub.2 H.sub.5                                                                               227-229                                             87          CH(C.sub.2 H.sub.5)C.sub.4 H.sub.9n                                                           154                                                 88          C.sub.9 H.sub.19 (mixed isomers)                                                              135-137                                             89                                                                                          ##STR98##     281-283                                             ______________________________________                                    

EXAMPLE 90

9.0 g of methyl iodide are added dropwise at room temperature to a suspension of 8.45 g (0.03 mol) of 4'-ethoxybenzimidazole-2-carboxanilide (from Example 12) and 2.3 g of potassium hydroxide in 90 ml of anhydrous ethanol in the course of 30 minutes. The reaction mixture is stirred at room temperature for 24 hours and poured onto 300 ml of water, the resulting mixture is filtered with suction, and the filter residue is thoroughly washed with water. 8.2 g of a colorless product of the formula ##STR99## having a melting point of 151° C. are isolated.

Analysis: C₁₇ H₁₇ N₃ O₂ (295.34). calculated: C 69.15, H 5.77, N 14.24, O 10.84. found: C 69.3, H 5.8, N 14.3, O 10.8.

EXAMPLE 91

5.5 g of potassium hydrogencarbonate and 7.1 g of 1-bromopropane are added to a solution of 14.1 g (0.05 mol) of 4'-ethoxybenzimidazole-2-carboxanilide (from Example 12) in 250 ml of dry dimethylformamide and stirred in at from 80° to 85° C. for 16 hours. The reaction mixture is filtered hot, the filter residue is washed with from 20 to 30 ml of dimethylformamide, and the solvent is drawn off in a rotary evaporator. The residue is dissolved in 100 ml of methanol by heating, and the solution is treated with active carbon, which is then filtered off. Cooling gives a crystalline precipitate of 12.7 g of a colorless solid of the formula ##STR100## Melting point 96°-97° C.

Analysis: C₁₉ H₂₁ N₃ O₂ (323.40). calculated: C 70.59, H 6.50, N 13.0, O 9.91. found: C 70.1, H 6.7, N 12.9, O 10.0.

EXAMPLE 92

Example 91 is repeated, except that benzyl bromide is used in place of 1-bromopropane, affording the following product of the formula ##STR101## Melting point: 157°-159° C.

Analysis: C₂₃ H₂₁ N₃ O₂ (371.44). calculated: C 74.39, H 5.67, N 11.32, O 8.62. found: C 74.1, H 5.7, N 11.5, O 9.0.

(B) APPLICATION EXAMPLES EXAMPLE 93 (Photostabilizing action in polyurethane)

The stabilizers listed in Table 7 are dissolved at 40°-50° C. in 150 g of polyetherol by stirring. The solution is intimately mixed with 76.5 g of a diphenylmethane diisocyanate formulation by stirring at 1,000 r.p.m. for 10-15 seconds. The mixture is immediately poured into a sealable mold, which has been preheated to 50° C., and is left for curing in the sealed state for 3-4 minutes.

Testing is carried out on foam sections having a continuous surface. The samples are exposed in a Xenotest® 1200 and assessed for yellowness in terms of the yellowness index (YI) as defined in ASTM D 1925. The results are given in Table 7, columns 3 to 6.

                  TABLE 7                                                          ______________________________________                                         Cycle in Xenotest 1200:                                                                        17 min exposure to light                                                       3 min exposure to water spray                                                  Temperature 45° C.                                                    Concen-       acc. to                                                          tration                                                                               YI      ASTM D 1925                                       Stabilizer      [%]      0 h    24 h 48 h 72 h                                 ______________________________________                                         7.1 Control         --       10.0 55.0 66.0 73.0                               7.2 Compound of Ex. 3                                                                              1.0      15.3 40.4 52.6 65.0                               7.3 Compound of Ex. 2                                                                              1.0      13.9 37.2 46.8 56.4                               7.4 Compound of Ex. 4                                                                              1.0      14.4 34.2 43.5 54.8                               7.5 Compound of Ex. 12                                                                             1.0      11.5 27.5 38.2 50.7                               7.6 Compound of Ex. 12                                                                             0.5                                                            + A*            0.5      10.0 30.1 37.2 46.8                                   + B**           0.5                                                        7.7 Compound of Ex. 12                                                                             0.5                                                            + A*            0.5      11.0 26.5 29.5 41.5                                   Triethylene glycol                                                                             0.5                                                            bsi-3-(3-t-butyl-4-                                                            hydroxy-5-methyl-                                                              phenyl) propionate                                                         7.8 2-(2'-Hydroxy-5'-                                                                              0.5                                                            methylphenyl)benzo-                                                            triazole                                                                       + C***          0.5      12.2 32.3 42.0 48.5                                   + Triethylene   0.5                                                            glycol bis-3-                                                                  (3-t-butyl-                                                                    4-hydroxy-5-                                                                   methylphenyl)                                                                  propionate                                                                 ______________________________________                                          ##STR102##                                                                     B** = Mixture of 1 part by weight of α-tocopherol + 10 parts by          weight of tris(nonylphenyl) phosphite                                          ##STR103##                                                               

EXAMPLE 94

The samples listed below in Table 8, which were prepared analogously to the method described in Example 93, were exposed in a Xenotest® 450 for 48 hours and assessed for yellowness in terms of the yellowness index as defined in ASTM D 1925.

                  TABLE 8                                                          ______________________________________                                                          Yellowness index according to                                                  ASTM D 1925 in Xenotest 450                                            Conc.   after                                                         stabilizer (% by wt.)                                                                               0 h         48 h                                          ______________________________________                                         8.1 Control    --        1.72      47.91                                       8.2 Compound of                                                                               1         5.79      20.81                                           Ex. 13                                                                     8.3 Compound of                                                                               1         1.91      18.23                                           Ex. 12                                                                     8.4 Compound of                                                                               1         3.59      19.15                                           Ex. 15                                                                     8.5 Compound of                                                                               1         2.89      12.88                                           Ex. 16                                                                     8.6 Compound of                                                                               1         5.11      21.11                                           Ex. 17                                                                     8.7 Compound of                                                                               1         10.04     26.76                                           Ex. 14                                                                     8.8 Compound of                                                                               1         6.58      21.68                                           Ex. 23                                                                     ______________________________________                                    

EXAMPLE 95

The procedure of Example 94 was used to test the following stabilizer combinations listed in Table 9 in PUR foam systems.

                                      TABLE 9                                      __________________________________________________________________________     Xenotest ® 450                                                                                        Yellowness index                                                               according to ASTM D                                                   Conc.    1925 in Xenotest 450 after                          Stabilizer        (% by wt.)                                                                              0 h   48 h                                          __________________________________________________________________________     9.1  Control      --       3.84  24.77                                         9.2  Compound of Ex. 12                                                                          0.5                                                               + A.sup.1    0.5      4.01  13.83                                              + B.sup.1    0.25                                                         9.3  2-(2'-Hydroxy-5'-                                                                           0.5                                                               methylphenyl)benzo-                                                            triazole                                                                       + A.sup.1    0.5      5.52  16.23                                              + B.sup.1    0.25                                                         9.4  2-(2'-Hydroxy-5'-methyl-                                                                    0.5                                                               phenyl)benzotriazole                                                           + C.sup.1    0.5      5.44  17.21                                              + Triethylene glycol                                                                        0.25                                                              bsi-3-(3-t-butyl-4-                                                            hydroxy-5-methylphenyl)                                                        propionate                                                                9.5  Compound of Ex. 16                                                                          0.5                                                               + A.sup.1    0.5      5.35  15.28                                              + B.sup.1    0.25                                                         9.6  Compound of Ex. 38                                                                          0.5                                                               + A.sup.1    0.5      5.19  15.40                                              + B.sup.1    0.25                                                         9.7  Compound of Ex. 12                                                                          0.5                                                               + D.sup.2    0.5      3.89  13.56                                              + B.sup.1    0.25                                                         9.8  Compound of Ex. 12                                                                          0.5                                                               + E.sup.2    0.5      3.45  12.59                                              + B.sup.1    0.25                                                         __________________________________________________________________________      .sup.1 A, B and C are as defined in Example                                    93                                                                             ##STR104##                                                                     ##STR105##                                                               

EXAMPLE 96

The series of test results below relates to further stabilizer mixtures prepared in PUR foam systems and exposed in a Xenotest® 450 for 48 hours.

                                      TABLE 10                                     __________________________________________________________________________                                        Yellowness index according to ASTM D                             Conc.         1925 in Xenotest 450 after                  Stabilizer mixture   (% by wt.)    0 h       48 h                              __________________________________________________________________________     10.1       Control   --            5.41      42.60                             10.2       Compound of Ex. 12                                                                       0.5                                                                  + A.sup.1 0.5           6.71      21.49                                        + B.sup.1 0.25                                                      10.3       F.sup.3   0.5                                                                  + A.sup.1 0.5           6.27      27.46                                        + B.sup.1 0.25                                                      10.4       Compound of Ex. 12                                                                       0.5                                                                  + G.sup.4 0.5           7.35      19.64                                        + B.sup.1 0.25                                                      10.5       Compound of Ex. 12                                                                       0.5                                                                  + H.sup.5 0.5           7.60      22.51                                        + B.sup.1 0.25                                                      __________________________________________________________________________      .sup.1 A and B are as defined in Example                                       93                                                                             ##STR106##                                                                     ##STR107##                                                                     ##STR108##                                                               

EXAMPLE 97

The samples listed in table 11 were prepared analogously to Example 93 and exposed in a Xenotest® 450 for 96 hours.

                  TABLE 11                                                         ______________________________________                                                               Yellowness index                                                               according to ASTM D                                                            1925 in Xenotest 450                                                   Conc.   after                                                    Stabilizer mixture                                                                             (% by wt.)                                                                               0 h    48 h  96 h                                    ______________________________________                                         11.1 Control        --        1.4  24.1  31.7                                  11.2 2-(2'-Hydroxy-5'-                                                                             0.5                                                             methylphenyl)-benzo-                                                           triazole                                                                       +Triethylene glycol                                                                           0.5       2.7  14.7  23.2                                       bis-3-(3-t-butyl)-4-                                                           hydroxy-5-methyl-                                                              phenyl propionate                                                         11.3 C.sup.1        0.5                                                             +Compound of Ex. 91                                                                           1.0       3.3  10.2  16.6                                       +Compound of Ex. 92                                                                           1.0       4.2  12.3  19.7                                  ______________________________________                                          .sup.1 Example 93: C                                                      

We claim:
 1. A photostabilized polymer containing as photostabilizer one or more compounds of the formula ##STR109## where n is 1 or 2,R¹ and R² or one of the radicals R¹ or R² are each independently of the other phenyl, pyridyl, furyl, quinolyl or thiophenyl, which each are unsubstituted or substituted by C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, halogen or trifluoromethyl, and the other of the radicals R¹ or R² is hydrogen, C₁ -C₁₂ -alkyl, C₇ -C₉ -phenalkyl or --COOR⁵, where R⁵ is linear or branched C₁ -₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl, where cycloalkyl and phenyl are unsubstituted or substituted by C₁ -C₄ -alkyl, or ##STR110## is a fused-on benzene ring which is unsubstituted or substituted by hydroxyl, halogen, C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, C₇ -C₉ -phenylalkyl, phenyl, --COOR⁶, --CO--R⁶, --CO--NH--R⁶, --COOH, --O--COR⁶, --NH--CO--R⁶, --SO₂ --R⁶ or --CN, where R⁶ is linear or branched C₁ -C₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl and the cycloalkyl and phenyl radicals are unsubstituted or substituted by C₁ -C₄ -alkyl, R³ and R⁴ are each hydrogen or one of the radicals R³ or R⁴ is C₁ -C₄ -alkyl or C₇ -C₉ -phenalkyl and,if n is 1, X (a) is phenyl, naphthyl or a 5- or 6-membered aromatic heterocyclic which may be benzofused, these radicals being unsubstituted or monosubstituted or disubstituted by C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, phenoxy, C₇ -C₉ -phenylalkoxy, C₇ -C₉ -phenylalkyl, trifluoromethyl, hydroxyl, halogen, --S--R⁷, --COR⁷, --COOR⁷, OCOR⁷, --COOH, --CN, --CONH--R⁷, --NH--R⁷, --N(R⁷)₂ or --NH--COR⁷, where R⁷ is linear or branched C₁ -C₁₂ -alkyl, C₅ -C₈ -cycloalkyl, phenyl or C₇ -C₁₀ -phenalkyl, in which cycloalkyl and phenyl are unsubstituted or substituted by C₁ -C₄ -alkyl, or if n is 2 X (b) is phenylene or naphthylene, these radicals being unsubstituted or substituted by C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy or halogen, or (c) is a radical of the formula ##STR111## where Y is a radical of the formula --(CH₂)_(m), --CO--, --CO--(CH₂)_(p) CO--, --OCO--(CH₂)_(p) COO--, --NH--CO--(CH₂)_(p) --CO--NH--, ##STR112## m is 1, 2 or 3, p is 0 or an integer from 1 to
 8. 2. A stabilized polymer as claimed in claim 1, wherein, in the formula, X is phenyl which is monosubstituted or disubstituted by C₁ -C₁₂ -alkyl, trifluoromethyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, C₇ -C₉ -phenylalkyl, phenoxy, phenyl, C₁ -C₁₂ -alkoxycarbonyl, C₁ -C₁₂ -alkylcarbonyl, benzoyl, cyano, N,N-di-C₁ -C₈ -alkylamino, C₁ -C₁₂ -alkylcarbonylamino, C₁ -C₁₂ -alkanoyloxy, benzoyloxy, C₇ -C₉ -phenylalkanoyloxy or chlorine.
 3. A stabilized polymer as claimed in claim 1, which contains as photostabilizer one or more compounds of the formula ##STR113## where T is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, trifluoromethyl, phenyl, C₇ -C₉ -phenalkyl or chlorine,R⁸ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, C₇ -C₉ -phenalkoxy, C₇ -C₉ -phenalkyl, trifluoromethyl, N,N-di-C₁ -C₆ -alkylamino, C₂ -C₁₂ -alkanoylamino, C₂ -C₁₂ -alkanoyloxy, benzoyloxy, C₇ -C₉ -phenalkanoyloxy, C₁ -C₁₂ -alkylcarbonyl, C₁ -C₁₂ -alkoxycarbonyl, benzoyl, cyano, methylenedioxy or ethylenedioxy, and q is 1 or
 2. 4. A stabilized polymer as claimed in claim 3, where, in the formula,T is hydrogen, methyl or chlorine, R⁸ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, trifluoromethyl or C₂ -C₁₂ -alkanoylamino and q is 1 or
 2. 5. A stabilized polymer as claimed in claim 1, wherein the polymer is a polyurethane.
 6. A stabilized polymer as claimed in claim 2, wherein the polymer is a polyurethane.
 7. A stabilized polymer as claimed in claim 3, wherein the polymer is a polyurethane.
 8. A stabilized polymer as claimed in claim 4, wherein the polymer is a polyurethane.
 9. A photostabilized polymer containing as photostabilizer one or more compounds of the formula ##STR114## where the two Rs are each independently of the other ##STR115## R⁸ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, phenoxy, C₇ -C₉ -phenalkoxy, C₇ -C₉ -phenalkyl, trifluoro-methyl, N,N-di-C₁ -C₆ -alkylamino, C₂ -C₁₂ -alkanoylamino, C₁ -C₁₂ -alkylcarbonyl, C₂ -C₁₂ -alkanoyloxy, benzoyloxy, C₇ -C₉ -phenalkanoyloxy, C₁ -C₁₂ -alkoxycarbonyl, benzoyl, cyano, methylenedioxy or ethylenedioxy,R⁹ is C₁ -C₁₂ -alkyl, C₁ -C₄ -alkoxy, chlorine or hydrogen, T is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, trifluoromethyl, phenyl, C₇ -C₉ -phenalkyl or chlorine, and q is 1 or
 2. 10. A stabilized polymer as claimed in claim 9, which contains as photostabilizer one or more compounds of the formula ##STR116## where R⁹ is methyl, methoxy or hydrogen,R¹⁰ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy or chlorine, and q is 1 or
 2. 11. A stabilized polymer as claimed in claim 9, which contains as photostabilizer one or more compounds of the formula ##STR117## where T' is hydrogen, methyl or chlorine,R¹¹ is C₁ -C₁₂ -alkyl, C₁ -C₁₂ -alkoxy, methylenedioxy, ethylenedioxy, trifluoromethyl, N,N-di-C₁ -C₄ -alkylamino, C₂ -C₁₂ -acylamino, C₂ -C₁₂ -alkanoyloxy, benzoyloxy or C₇ -C₉ -phenalkanoyloxy, and q is 1 or
 2. 